With the continuous developments in the field of display technology, the liquid crystal display device has been widely applied in electronic products, such as smart phone, panel computer, and laptops. However, since the liquid crystal panel itself does not have the function of emitting light, it is generally necessary to use a backlight source as the light source to implement the display function.
The light guide plate is one of the key components of the backlight source. In the injection and molding process of the light guide plate, after the plastic raw material is melted, it is injected into the mold cavity at a high speed in the high temperature state, hence, the plastic raw material will be carbonized in the strong shear thermal state, which may result in physical property changes. Thus the light emitted by the molded light guide plate will have non-uniform spectrum, such that the problem of color yellowing may occur to the backlight source. In addition, when spraying or printing mesh points on the light guide plate, and performing UV curing to the light guide plate sprayed or printed with mesh points, the UV glue may also produce yellowing effect via UV irradiation, and result in color yellowing of the backlight source.
In order to improve the above problem, the commonly used solutions in the prior art include: (1) using a light guide plate material with higher flowability so that the difference between the carbonization degrees of the material that flows previously and the material that flows subsequently after cooling will be reduced, thereby enabling the color temperature deviation of the light guide plate to be reduced, and mitigating the problem of color yellowing of the backlight source to a certain extent; (2) performing injection moulding after reducing the material temperature and increasing the mould temperature appropriately. When injection molding the light guide plate, the influence of the mould temperature to the light guide plate is smaller than the influence of the material temperature to the light guide plate. Hence, performing injection molding after reducing the material temperature and increasing the mould temperature appropriately will enable the color temperature deviation at different parts of the light guide plate to be reduced, and mitigate the problem of color yellowing of the backlight source to a certain extent; and (3) When performing injection molding, filling the interior of the injection molding machine with nitrogen to prevent the raw material from being oxidized due to contacting with the oxygen, which can also improve the color temperature deviation problem at different parts of the light guide plate, thereby mitigating the problem of color yellowing of the backlight source.
However, the above solutions can only mitigate the color yellowing problem of the backlight source in a very small degree, and cannot eliminate color yellowing of the backlight source effectively.